Advances in the field of high speed material processing have created new and improved uses for surface finishing. Examples of high speed processors which have recently proved successful in the industry are available from Mikronite Technologies, Inc., and are disclosed in U.S. Pat. Nos. 5,355,638, 5,848,929, 6,599,176, 6,733,375 and PCT/JUS03/21218, which are all incorporated herein by reference in their entirety. The centrifugal finishers disclosed in those patents include an outer vessel or housing and at least one, and in many cases several, inner vessels located within the outer vessel. The inner vessels are revolved around the inside surface of the outer vessel while concomitantly rotating about their own axes. A traction surface is preferably included between the inside surface of the outer vessel and the outside surface of the inner vessel. The traction surface provides a frictional interface that assists in rotation or rolling of the inner vessel along the surface of the outer vessel, while the inner vessel experiences centrifugal forces. The forces, in turn, are transferred to finishing media located within the inner vessel, thereby providing high speed polishing of the products contained in the inner vessel. As described herein, the terms polishing and finishing are intended to cover not only fine removal of surface particles, but also coarse removal of material which is more akin to a sanding operation. Thus, the term is intended to cover altering the surface of an article.
The speeds at which these devices operate are extremely high. In particular, the media within the vessels in these machines experience consistent accelerations in excess of 16 g's, and can be as high as above 120 g's. These high speeds are very beneficial in a finishing process since they permit the finishing media to perform efficient finishing of the entire surface area.
As discussed in U.S. Pat. No. 6,863,207, which is incorporated herein by reference in its entirety, the higher speeds and accelerations that can be obtained with these systems open up the use of surface finishing to other material processing operations. In particular, U.S. Pat. No. 6,863,207 describes how current welding operations can be improved with the use of high speed centrifugal processing. The patent specifically describes how the creation of a vacuum within the processing vessel can assist in welding of materials. In one example, cobalt malt is mixed with tungsten carbide to make inserts for tools. Currently, this combination can only be achieved when subjected to high temperatures and high pressure.
While U.S. Pat. No. 6,863,207 discloses a system for generating a vacuum inside a vessel during a rotational processing procedure, further benefits can be provided by controlling the environment within the vessel. For example, in a centrifugal tumbling/polishing system, high energy is imparted in a cascading motion to produce controlled friction, resulting in abrading and surface refinement as well as sub-surface compression. During the processing, considerable heat is developed. Such heat may not be desirable during the processing, or in certain cases, it may be desirable to increase and/or focus the heat energy during the processing. In addition it may be desirable to introduce a gas or complex atmosphere in order to accelerate a chemical reaction or form a coating on the article. Thus, further processing benefits can be achieved if the environment within a processing vessel can be controlled.